Inside Britain's best-known mosque, a pillar of moderate respectability, the faithful have just heard Sheikh Saeed Radhwan give a calm, erudite discourse on the nature of worship in Islam.

Outside, the message is simple, direct, and aggressive: "Who is the terrorist? Bush is the terrorist!" shouts one protester, flanked by posters of Afghans killed or injured in recent bombing raids.

A few hours earlier, on the other side of the world, Irfan Shah had also attended noon prayers - in Islamabad, the capital of Pakistan. He had heard a more political sermon, urging Muslims to defend their brothers in Afghanistan against aggression.

"There has always been politics in the sermons," said Mr. Shah, a clean-shaven computer specialist dressed in Western clothes. "Sometimes I agree, sometimes I don't agree. But in Islam we can all think what we like."

The Friday prayers in mosques from London to Cairo to Islamabad are one way to take the global pulse of Islam. What's clear from these, and from interviews with Islamic scholars and leaders, is that the level of tension within the one-billion-member Muslim community is growing. The drama and scale of the tragedy of Sept. 11 have inspired some moderate Muslim leaders to gird their loins for fresh combat with their extremist co-religionists.

Yet, it's also apparent that, for the moment, the voices of moderation are few - and often conflicted. They condemn the terrorist attacks on the US as a violation of Islam. But many have long been critics of US foreign policy, and the current military retaliation in Afghanistan - a Muslim nation - is a hard sell to their followers.

"The images of children being killed - they are drowning out the people who talk about what happened on Sept. 11," said Ahmed Khan as he left the London mosque Friday, like most others paying only passing attention to the protesters. "Even the moderates are growing more angry about what is happening in Afghanistan."

That view is widely echoed across the Islamic world, where an instinctive closing of Muslim ranks makes it hard for moderates to criticize other members of the faith, however wrongheaded and dangerous they think they are.

In Egypt, says Fahmi Howeidi, a columnist at the semi-official Al Ahram newspaper and a prominent spokesman for nonviolent Islamists in Cairo, "I'm afraid that people have mostly forgotten Sept. 11, and now they are talking about Oct. 7," the day when the United States and Britain began bombing Taliban targets in Afghanistan.

That was clear enough at Friday prayers in Cairo three weeks ago, just after the bombing began. From the pulpit at Al Azhar mosque - the most respected seat of Islamic learning in the world - Grand Sheikh Mohammed Sayed Tantawi told his audience that "it is the right of the country that has been attacked to retaliate, but it shouldn't kill innocent people."

But as soon as he had finished his sermon, worshippers took the microphone to call for a holy war against America, which they accused of launching a war against their religion.

Despite the best efforts of US leaders from George Bush on down to deny that the war against terrorism is a war against Islam, Muslims everywhere are afraid that this is just what the campaign has become. Poor and powerless, most of them already resent America's sway over large parts of the world, and that resentment feeds a readiness to see Washington as the enemy when bombs start falling on fellow Muslims.

"People sympathized with Americans before, but now there is a feeling they are making the same mistake and killing innocent people," says Mr. Howeidi, the Egyptian columnist. "In certain circumstances you can convince people with moderate arguments, but under different circumstances they won't listen."

Moderate Islamic leaders all over the Middle East "are between a rock and a hard place right now," says John Esposito, who heads the Center for Christian-Muslim Understanding at Georgetown University in Washington, D.C. "President Bush has given them a polar choice - they are with us or they are against us. Many of them are totally against what happened on Sept. 11, but they are not going to be thrilled if the war against terrorism is broadened to attacks on other countries," such as Iraq.

A one-page flyer, stacked in a pile on a shoe rack at the London mosque, made the same point. "Bin Laden and Bush have both called on the world to be 'either with us or against us' " read the anonymous protest, titled "Bombing and killing and assassination do not win hearts and minds."

"The free-thinking citizens of the world reject both these simplistic calls," it continued. "We condemn the loss of innocent lives, wherever it occurs. We appeal to our leaders to stop this mad war immediately and instead make a stand for diplomacy, justice, and the rule of law."

Even in Paris, where the mood is calmer than in many Middle Eastern capitals, the director of the Great Mosque, Dalil Boubakeur, has judged it wiser to instruct his imams not to speak out too bluntly against the radicals just yet. "The train is still going at 120 miles an hour," he says. "We have to wait for things to cool down. For the time being, our sermons are calling on people to reflect and to be vigilant."

That is not a terribly dramatic or appealing message when set against the stirring calls for jihad that Dr. Boubakeur says "are ravaging our young people." The devil, he says, has all the best tunes.

And they are especially catchy among disaffected, frustrated and disillusioned people, who can be found by the tens of millions in poor and struggling Muslim countries. It is their despair that makes the radicals' interpretation of jihad so appealing, although orthodox Muslim scholars universally have repeated time and again in recent weeks that, properly understood, jihad is acceptable only as a defensive war against aggression.

But that hasn't stopped Taliban leaders and Osama bin Laden from calling for Muslim support. The latest video-taped recording was broadcast Saturday by the al-Jazeera television channel. "It is fundamentally a question of a religious war ... the peoples of the East being Muslims, and those of the West being Christians," said renegade Saudi millionaire Mr. bin Laden. He called on Muslims to "defend their religion and their brothers in Afghanistan" against the "crusade" being led by the US.

In the West, the destruction of the World Trade Center has galvanized some Muslim leaders to raise their voices publicly against the vitriolic strain of Islam that bin Laden has espoused.

And yesterday, Amr Mussa, the head of the Arab League, resoundingly rejected bin Laden's call to join in a "religious" war against the Christian West. "Bin Laden does not speak in the name of the Arabs and Muslims," Mr. Mussa told journalists in Damascus.

"I now feel responsible to preach, actually to go on a jihad [holy war] against extremism ... and to urge other religious leaders" to do the same, says Siraj Wahaj, the imam of the Tawqa mosque in Brooklyn, New York, and a prominent voice in American Islam.

"Up to now, people would speak frankly about Muslim governments or movements within the [American Muslim] community, yet were reluctant to criticize publicly," adds Ingrid Mattson, vice president of the Islamic Society of North America. "But that's all changed."

Outside America and Europe, however, Muslim condemnations of the Sept. 11 events have often been muted or hedged.

In many Islamic countries, in fact, significant numbers of people refuse to accept that bin Laden, or any other Muslim, was responsible for the attacks, preferring to believe conspiracy theories blaming them on Israel or on other culprits.

Rare are the authoritative voices from mosque pulpits or TV studios prepared to confront Muslim audiences with the thought that "there are people in Islam who are ready to do this sort of thing, and this is where we have to start with our self-criticism," as Tariq Ramadan - a leading advocate of Islamic reform in Europe - puts it.

Mr. Ramadan, based in Geneva, argues in his books and lectures that Muslims must condemn the use of force, and embark on theological reforms to encourage a less literal reading of the Koran than fundamentalist Muslims advocate.

Only that kind of "Islamic Reformation," he says, can modernize his religion so that it embraces the scientific and social changes that have transformed the world since Islam's holy texts were written, but which extremists reject as haram, or forbidden.

In a religion that has no papacy or other central authority to lay down the law, Islamic scholars, writers, and imams in many Muslim countries have argued on and off for decades in favor of such changes, hoping they would open up their religion to broader influences.

But they have never succeeded in gathering much popular support. "The voices in favor of authentic pluralism are not nearly sufficient among Muslims," says Farid Esack, a South African Muslim theologian who was Nelson Mandela's minister for gender equality.

"Today I see a debate opening, but only among a few individuals," worries Malek Chebel, a Paris-based French-Algerian scholar whose own eclectic interests are evident from his crowded bookshelves, where a tome on Sufi mysticism sits between a biography of Jimi Hendrix and a book about war in cyberspace.

Dr. Chebel and others like him, who call themselves "moderates" or "modernizers" or "tolerant Muslims," complain that one of their problems is a lack of money and other resources.

Wealthy businessmen from Saudi Arabia and other Gulf countries - some of them members of ruling royal families - have poured hundreds of millions of dollars into charities that have built mosques and religious schools promoting Wahhabism, a particularly austere version of Islam, all over the world, from Bosnia to Malaysia, from the US to Chechnya.

It was Saudi money, too, that funded the religious schools in Pakistan where the Taliban movement was born.

"We don't have petrodollars to promote liberal Islam," laments Boubakeur, of the Grand Mosque in Paris. "It would help if they just cut off their support to the others," the radical Islamic ideologists, he adds.

Though the vast majority of ordinary Muslims everywhere are as constitutionally pre-disposed to moderation as anyone else, moderate-minded leaders are not anywhere near as active as their radical colleagues when it comes to organizing storefront mosques, setting up neighborhood clinics, or establishing simple schools.

"We express ourselves in books and in universities, but not on the street," acknowledges Chebel. "We have to reform our methods. If we are not heard, it is partly our own fault."

On the other side of the world, Ulil Abshar Abdallah, an official of Nahdlatul Ulamam, Indonesia's largest Muslim organization, agrees. "We've been terrible communicators," he says. While traditional Indonesian Muslim leaders were mulling over religious paradoxes and disputes about the lives of long-dead saints, "radical Muslims have been presenting a simple yet comprehensive ideology that can be grasped by common people."

Mr. Ulil and like-minded religious leaders - both Christian and Muslim - recently created the Indonesian Council on Religion and Peace to counter a tide of intolerance that was rising even before the US war on Afghanistan began. So far the council's work consists of brainstorming sessions in search of effective ways to get that message out. "It's not an easy battle we're fighting," he says.

Mehmet Aydin, a theology professor at the September 9th University in Istanbul in Turkey, says that while the radicals are often visible, "the other [moderate] voices do not have this history ... of rushing out into the street to express your anger, so perhaps they do not come out as strongly as we would like,"

In some countries, such as Saudi Arabia or other Gulf sheikhdoms, it is simply forbidden for anyone to take to the streets to protest the state religion. In others, like Egypt and Algeria, where armed Muslim radicals have battled government forces - and intellectual enemies - for years, many moderates are simply too scared of being killed to stand up and be counted.

That fear has spread far and wide. In Pakistan, says a young man who - tellingly - asked not to be named, "it used to be quite OK to publicly criticize a mullah. It was normal. But now I keep silent. The man sitting next to me - I don't know where he stands. And he could take my name to the [militant] brothers."

In Cairo, Said al-Ashmawi, a former judge who has spent the past 20 years speaking out against Islamists seeking to shape Egypt's political life according to Islamic precepts, has needed a police bodyguard for those 20 years. "People like me are intimidated," he says. "Who dares to put himself in such a critical situation?"

And in Algeria, where the Armed Islamic Group has been blamed for tens of thousands of killings, debate among different schools of Islam "practically stopped 10 years ago, when the violence broke out, because everyone was too frightened to publish," says Boubakeur of the Grand Mosque in Paris. "It is terrible, the inquisition that has gone on in Muslim countries."

In a broad, tasteful sitting room in a wealthy Islamabad neighborhood, Fakher Imam and his guests are fighting against religious extremism in a more genteel fashion, over cups of tea, .

The problem, they agree, is not the extremists' religion, or even their idea of holy war. It is that many of them are so poorly educated that they are not aware of the deeper concepts of the religion they claim to defend.

"In Islam there are two jihads," explains Ahmad Raza Qasuri, a lawyer with a booming voice who argues cases before Pakistan's Supreme Court. "Fighting against a known enemy, someone who's behind that hillock or that tree, is minor jihad. The major jihad is against the demons inside of you."

Only better and more modern religious education can spread that kind of teaching, say opponents of Islamic radicals.

"Give me the media," demands Dr. al-Ashmawi, the Egyptian judge. "Give me a weekly half-hour program on television, interview me in the newspapers. If enough of us are aired enough, we can make a wave of enlightenment."

Imam Esack, the former South African government minister, worries that the problem goes deeper than that. "We have a history of wanting to dodge radical questions," he says of his fellow Muslims, "so we tend to go for simplistic lines," such as the insistence that Islam is a religion of peace.

"The major problem Muslims have is not that there is a single power that has hegemony in the world," such as the US, "but that we are not that single power," Esack argues.

Soheib Bensheikh, the Grand Mufti of Marseille - a French Mediterranean port that is home to many North African Muslims - is also skeptical. "Our religious thinkers lack weight and rigor and daring," he complains. "The modernists have developed nothing in their body of thought to support their affirmations that Islam is a peaceful and fraternal religion."

In the Arab countries of the Middle East, where almost all the governments outlaw free speech, it is perhaps not unsurprising to find a lack of the sort of intellectual vigor that Dr. Bensheikh is looking for.

For example, in Egypt, where the government has clamped down on any signs of political Islam, whether violent or not, moderates have had a hard time developing or spreading their thought, complains Howeidi, the Egyptian columnist.

"Our governments are busy with one thing, fighting extremism," he says. "But they have done nothing to support a moderate way of thinking, and legal restrictions mean moderates can't set up parties or other organizations."

"We are fighting on two fronts," he adds. "Against the extremists, and against undemocratic political pressure from our governments."

It is that sort of difficulty, says Dr. Ramadan in Paris, that puts such a heavy responsibility on Muslims in Western countries, where they enjoy the political freedoms they need to open up a debate with their co-religionists elsewhere in the world.

"Over the last 10 years, in Europe and in America, we have developed a completely new understanding of the West, which is not hostile," he says. "If a clash of civilizations is going to be avoided, it is up to us in the West."

That's a view echoed by many American Muslims, who say they can play an important role in portraying America more positively, and more accurately, to their Muslim brothers and sisters abroad. But they say that a more sympathetic mood in America would help them do this.

They also insist that they will only be credible abroad if they express themselves honestly - and that generally means criticizing aspects of US foreign policy. But if they silence their criticisms to avoid charges of treachery from their neighbors, moderates say they will not be taken seriously in the Muslim world.

"Muslim-bashing and profiling are absolutely counterproductive because they force Muslims to put their heads down and deal with harassment," says Mohiaddin Mesbahi, an Iranian-American who teaches security studies at Florida International University. "Only if they feel confident and welcome as Americans can [American Muslims] become important ambassadors of Islamic thinking," he adds.

And there is a lot of Islamic thinking going on in America, trying to mesh traditional Islamic precepts and principles with the realities of today's world.

"American Muslims have shouldered the responsibility to try to formulate an Islamic jurisprudence suitable for the 21st century," says Azizah al-Hibri, a professor at the University of Richmond School of Law, who has helped draft Qatar's new laws on women's rights and the family. "And this is an era of democracy, free thought, and peaceful conflict resolution."

One result of this work: a 600-page volume of articles on Islamic law, published last month in the Journal of Law and Religion of the Hamline University School of Law in St. Paul, Minn., that is aimed at stirring debate throughout the Muslim world. One highlight of the volume: a detailed exploration of Islamic jurisprudence by a Syrian thinker who rejects the use of violence or coercion.

America, perhaps naturally, is one of the countries where Muslims have raised their voices most loudly to condemn those who perpetrated the attacks on Sept. 11.

Standing on the White House lawn with President Bush a few days after the destruction of the World Trade Center, one of America's most prominent and influential Muslim scholars, Hamza Yusuf, spoke for all his fellow moderates when he lamented that "Islam was hijacked on that Sept. 11, 2001, on that plane as an innocent victim."

On the website Beliefnet.com, Ingrid Mattson, who teaches Islamic studies at Hartford Seminary, Hartford, Conn., wrote recently that she had "not previously spoken about suicide attacks committed by Muslims in the name of Islam.... This was a gross oversight," she acknowledged.

"I should have asked myself, who has the greatest duty to stop violence committed by Muslims against innocent non-Muslims in the name of Islam?" she wrote. "The answer, obviously is Muslims."

Reporting by staff writers Scott Baldauf and Robert Marquand in Islamabad, Pakistan, Ilene R. Prusher in Cairo, Jane Lampman in Boston, as well as special correspondents Dan Murphy in Jakarta, Indonesia, and Nicole Itano in Istanbul, Turkey.